Background: The Northern California Pediatric AIDS Treatment Center (NCPATC) was formed in 1988 and includes 3 sites. The University of California, San Francisco (UCSF) provides access to trials to HIV exposed and infected infants, children and adolescents, as does Children's Hospital Oakland (CHO). The Bay Area Perinatal AIDS Center (BAPAC) at San Francisco General Hospital and at UCSF provides access to trials to HIV infected pregnant women and their infants. BAPAC recently expanded to the East Bay AIDS Center; infants born to women enrolled through this program are referred to CHO for ongoing care. The Larkin Street Youth Center (LSYC), founded in 1984, has provided HIV care to street involved and homeless youth since 1990. Since 1998, LSYC, the UCSF Division of Adolescent Medicine, and the UCSF Pediatric AIDS program have collaborated in a Title IV funded center for the care of HIV + youth. LSYC is the major adolescent component of this application. An Adolescent Trial Network application for LSYC was submitted and funded. Research Objectives: The NCPATC brings focused expertise in immunology and vaccines to the PACTG. Proposals include 1) comparison of recent thymic emigrants to lymphocytes undergoing cell death through apoptosis in order to assess the quantitative role of the thymus gland in immune restoration; 2) assessment of CD4 specific lymphoproliferative activity to HIV, as well as other antigens; CD8 cytotoxic lymphocyte activity to HIV, and CD8 non-CTL HIV specific immunity; 3) augmentation of immune restoration by GM-CSF in children with residual virus while on HAART; 4) re-assessment of autologous neutralizing antibodies for use with vaccines in neonates. Dr. Wara's membership on HIVNET 027 provides linkage with the PTN whereas co-chairing the Vaccine Adolescent Working Group provides linkage with the VTN. Patient Population: With the proposed expanded network, access to patients for enrollment to PACTG trials includes 90 infants (0-23 mo) of whom 5 are infected; 142 HIV infected children age 2-12 years; 84 HIV-infected adolescent males and 50 infected adolescent females. Thirteen newly identified HIV-infected infants and children were referred to the network during the past year. Forty HIV-infected pregnant women each year deliver through BAPAC/EBAC. Research Contributions: Members of the NCPATC have chaired/co-chaired four protocols, provided immunology or pharmacology expertise to 12 protocol teams, and have been team members of nine protocols. Dr. Wara chaired the Immunology/IBT RAC; she and Ms. Trevithick served on the Executive Committee, NCPATC members have authored 13 PACTG primary publications.